Fuse powder composition

ABSTRACT

NOVEL FUSE POWDER COMPOSITIONS WHICH BURN VERY RAPIDLY WITHOUT DECOMPOSITION COMPRISE ZIRCONIUM, BARIUM CHROMATE, AMMONIUM PERCHLORATE, AND AMMONIUM DICHROMATE.

May 21, 1974 BERTRAND ET AL $811,969

FUSE POWDER COMPOSITION Filed March 7. 1972 United States Patent Ofice 3,811,969 FUSE POWDER COMPOSITION Yves Bertrand and Robert Grebert, Saint-Medard-en- Jalles, France, assignors to Etat Francais represente par le Ministre dEtat Charge de la Defense Nationale, Paris, France Filed Mar. 7, 1972, Ser. No. 232,493 Claims priority, application France, Mar. 8, 1971, 7107863 Int. Cl. C06b 11/00 US. Cl. 149-20 Claims ABSTRACT OF THE DISCLOSURE Novel fuse powder compositions which burn very rapidly without decomposition comprise zirconium, barium chromate, ammonium perchlorate, and ammonium dichromate.

The present invention relates to fuse powder compositions for pyrotechnic charges. The fuse powder composition of this invention comprises: (a) zirconium, and (b) a mixture of barium chromate, ammonium perchlorate and ammonium dichromate, the proportions of the constituents being such that the oxygen balance is equilibrated between the zirconium and the said salts, that is, after the powder is ignited in a closed bomb, after combustion, no oxygen remains.

Preferably, the new compositions contain: 33 to 57% by weight of zirconium, 27 to 41% by weight of barium chromate, 11 to 17% by weight of ammonium perchlorate, and 5 to 9% by weight of ammonium dichromate. An especially preferred composition contains 45% by weight zirconium, 34% by weight barium chromate, 14% by weight ammonium perchlorate, and 7% by weight ammonium dichromate.

The zirconium used advantageously has an average particle size of 3.4 microns, a specific surface area of 2,700 cm. /g., a non-compressed density of 1.1 and a compressed density of 2.

The barium chromate used preferably has a particle size of 2.9 microns, the ammonium perchlorate a particle size of 12 to 13 microns, and the ammonium dichromate a particle size of 110- microns.

In order to prepare the new compositions, the ingredients are mixed together in the proportions indicated, for example, by means of a Moritz mixer revolving at slow speed for 1 hour, in a chamber held at a tempera ture of 2l29 C., and a relative humidity of 30-40%. After mixing, the mixture is stored in hermetically sealed boxes.

The fuse powder composition of the invention shows the following advantageous characteristics:

(a) It has a very high speed of combustion, of the order of several hundreds of metres/second, higher than that of known fuse powders; the time interval between the electrical impulse which triggers the ignition, and the pressure rise caused by the combustion of the fuse powder, is of the order of 5 milliseconds, while this time is never less than 15 milliseconds for other known fuse powders;

(b) in spite of its high speed of combustion, it does not detonate; and

(c) it can burn in a high residual vacuum; tests have shown that it burns in a vacuum of 3X10 Hg, corresponding to an altitude of 75 km. (mesosphere). Conventional fuse powders do not burn at a pressure of less than about 50 mm. Hg.

Such characteristics render the new powder compositions useful in the following applications: rapid lighting of powder-fired gas generators; and lighting of solid rocket propellants at high altitude.

3,811,969 Patented May 21, 1974 A view in perspective of a fuse for a powder-fired gas generator, the cover of which has been raised to show the inside of the fuse, is shown in the only figure of the accompanying drawing. The fuse consists of a toroidal case 1 of nitrofilm [i.e. celulose nitrate film containing a plas ticizer (stearate) and a stabilizer (centralite)], reinforced with polyamide fibres in the side walls, and closed by a cover 3, also toroidal and of nitrofilm. This case, of external diameter 70 mm. and thickness 5 mm., contains 5 g. of the new fuse powder composition 3, and two electrical igniter beads 4, diametrically opposite and embedded in the powder. Orifices 5 are provided in the case 1 for the passage of electrical wires 6 connected to the igniters. Such fuses are particularly suitable for lighting solid propellant charges in hollow strands mounted on an annular base which are used in the gas generators described in United States Patent Application No. 206,662, filed Dec. 10, 1971, and 205,046 filed Dec. 5, 1971.

The operation of the fuse is as follows: an electrical impulse is sent in the wires 6 connected to the igniters 4. The latter comprise a lighting head, for example of a fulminate, fixed to an electrical resistance. The latter, by heating, ignites the head, which itself ignites the fuse powder. The bottom of the case of nitrofilm burns in its turn, and the heat generated ignites the solid propellant.

As mentioned above, one of the advantages of the new powder compositions compared with conventional fuse powders is their speed of ignition. Usually, the speed of ignition of a fuse powder is characterized by two parameters: d the delay which elapses between the lighting signal and the appearance of a pressure rise caused by the beginning of the ignition of the fuse powder; and d the delay which elapses between the moment of appearance of this pressure rise and the moment when this pressure is at a maximum. The delay d characterizes the sensitivity of the fuse powder and the delay d; the speed of combustion of this powder.

The table which follows gives the delays d, and d of the powder according to the invention and those of two conventional rapid fuse powders:

The test was carried out under normal conditions on a fuse plug containing 10 g. of fuse powder.

Powder composition according to the invention Powder 1 Powder 2 ch in milliseconds dz in milliseconds Furthermore, for igniting solid blocks of propellant at high altitude, a fuse is used such as that described in US. Pat. No. 3,581,662 in which the primary lighting charge of black powder is replaced by the powder composition of the present invention.

Conventional primary lighting charges do not burn at pressures of about 50 mm. Hg or below while the new powder compositions can burn in a vacuum as low as 0.03 mm. Hg corresponding to an altitude of km.

The table which follows gives the results of firings of the new powder compositions at simulated high altitudes.

Conventional primary lighting charges do not operate at such low initial pressures.

The fuse comprises 50 g. of the new powder composition placed in the front third of the central channel of a propellant block to be ignited. The blocks used are composite propellants with a polybutadiene binder.

We claim:

1. Fuse powder composition comprising (a) zirconium and (b) a mixture of barium chromate, ammonium perchlorate and ammonium dichromate, the proportions of the constituents being such that the oxygen balance is equilibrated between the zirconium and the said salts.

2. Composition according to claim 1, comprising 33 to 57% by weight of zirconium, 27 to 41% by weight of barium chromate, 11 to 17% by weight of ammonium perchlorate, and to 9% by weight of ammonium dichromate.

3. Composition according to claim 2, comprising 45% by weight of zirconium, 34% by weight of barium chromate, 14% by weight of ammonium perchlorate, and 7% by weight of ammonium dichromate.

4. Composition according to claim 1, in which the zirconium has an average particle size of 3.4 microns, a specific surface area of 2,700 cm. /g., a non-compressed density of 1.1 and a compressed density of 2.

5. Composition according to claim 1 in which the barium chromate has a particle size of 2.9 microns, the ammonium perchlorate has a particle size of 12 to 13 microns, and the ammonium dichromate has a particle size of microns.

References Cited UNITED STATES PATENTS 3,l73,367 3/1965 Shinpaugh 149-40 X 3,454,437 7/1969 Yamazaki et a1. 149-42 X 3,553,039 1/1971 Keenan et al l49-42 X 3,725,516 4/1973 Kaufman 149-40 X 3,734,788 5/1973 Kaufman 149-42 X STEPHEN J. LECHERT, JR., Primary Examiner US. Cl. X.R. 

